The present invention relates to a control system, and method of operating same, for controlling the application of pressure to a diaphragm pump. The system automatically, and continuously, adjusts the pressure utilized in actuating the diaphragm within the diaphragm pump so as to maintain a constant flow of the fluid passing through the diaphragm pump.
Conventional prior art industrial control systems, that are currently utilized with diaphragm pumps, require that a pressure regulator be manually adjusted. Consequently, if the discharge conditions change, the pressure regulator must be changed by manual manipulations performed by a human operator.
As can readily be appreciated, failure to properly adjust the diaphragm pump results in inefficient operation of the pump. For example, if the pressure regulator is set too low for the discharge conditions, incomplete pump strokes with a resultant low flow rate will occur. Conversely, if the pressure regulator setting is too high for the discharge conditions, the pump may be damaged. The instant control system overcomes these deficiencies by automatically, and continuously, adjusting the pressure setting to produce proper operating conditions and obviates the need for a human operation to monitor and manually adjust the pressure regulator. The control package, and the diaphragm pump operated thereby, find particular application in filling a fixed volume in which the pressure increases as the volume is filled; an exemplary application would be found in a plate and frame filter press, although several other applications are envisioned.
U.S. Pat. Nos. 4,705,462 and 5,076,890, both granted to Balembois and both assigned to the assignee of the present invention, are illustrative of known methods utilized to control the pumping action of a fluid actuated diaphragm pump. Balembois '462 utilizes a sensing structure which is implemented to control the functional parameters of the diaphragm pump. For example, such arrangement controls the initiation and duration of applied fluid pressure, the discharge time and the complete cycle time. Balembois '890 is an improvement over the earlier Balembois '462 patent. In addition to sensing the cycle time of the diaphragm pump, the apparatus measures the volumetric flow rate, and adjusts the cycle time to correct any deviations from a predetermined volumetric flow rate.
The use of control systems in an artificial blood circulation assembly is disclosed by Bosio in U.S. Pat. No. 4,212,589. The apparatus includes a pump having a fluid driven tubular member. The fluid driving pressure is automatically regulated based upon the opening and closing of a timing switch. The timing switch is operated by a feeler which follows the deformation of the tubular member as fluid pressure acts on the tubular member. The feeler operates the switch to close the circuit of an optical signalling device when deformation of the tubular membrane reaches a predetermined value.
U.S. Pat. No. 4,966,528, to Henkel et al. discloses an apparatus for controlling the hydraulic circuit of a piston diaphragm pump. The apparatus includes a sensor for measuring the length of the stroke travel of the diaphragm and generating a corresponding stroke travel signal that is transmitted to a control means. The control means then compares the stroke travel signal with the predetermined stroke values. If the stroke travel signal deviates from the predetermined stroke values, the amount of hydraulic medium per time unit is accordingly adjusted.
U.S. Pat. No. 4,856,969, to Forsythe et al, discloses a diaphragm pump having a timer for controlling the cycle time of the diaphragm pump and an adjustable pressure regulator. Additionally, Ruoo (U.S. Pat. No. 3,814,548) and Mandroian (U.S. Pat. No. 4,265,600) disclose diaphragm pumps having regulation assemblies.